Nickel base superalloys are commonly employed for gas turbine engine components such as shafts and disks. As a result of the demand for improved performance and efficiency, the components of a modern gas turbine engine operate near the limit of their properties with respect to temperature, stress, and oxidation/corrosion. Due to these aggressive operating environments, the superalloy materials from which the components are made must possess a combination of exceptional properties including high strength capability at elevated temperatures and rotational speeds.
In particular, nickel base superalloy articles suitable for components such as shafts and disks must possess superior low cycle fatigue strength because repeated cycling between full engine power and idle induces a cycle of thermomechanical stress within the engine. Such superalloy articles must possess superior low cycle fatigue strength in order to withstand such conditions.
Superalloy articles for components such as disks are typically machined to bring them to finished geometry. For example, billet material or a forged component may be inserted into a lathe wherein a tool insert removes layers of superalloy material, while the component spins, until the correct geometry or diameter is achieved.
A problem, however, with some prior art machined disks, particularly lathe turned disks using tungsten carbide tool inserts, is that they display low cycle fatigue failures at relatively low lives, under testing conditions.
Accordingly, there exists a need for machined nickel base superalloy articles having superior low cycle fatigue strength.